Soil erosion risk assessment; Financial approach :: Case study in a sub-catchment of Progo watershed Central Java, Indonesia

SETIAWAN, Muhammad Anggri, Dr. Hartono, DESS

2006 | Tesis | Magister Geo-Informasi Manajemen Bencana

Resiko erosi tanah telah menjadi sebuah permasalahan dalam bencana alam yang layak diperhitungkan mengingat keberadaanya yang telah menimbulkan banyak dampak negatif. Kondisi tersebut kembali diangkat dalam penelitian ini yang mencoba untuk memberikan sebuah gambaran lain dalam metode perhitungan resiko erosi tanah. Perolehan nilai dari resiko erosi tanah yang dapat dipercaya membutuhkan ketersediaan intitrmasi bahaya erosi yang akurat. Pengukuran bahaya erosi yang eukup rumit telah menyebabkan ketidakpastian dalam nilai yang diperhitungkan karena tergantung dari pemilihan metode. Pemodelan dalam erosi kemudian dijadikan sebuah metode yang sering digunakan di antara metode yang lain karena faktor dari efisiensi waktu dan biaya. Penerapan sebuah model harus memperhitungkan kondisi ketersediaan data suatu daerah penelitian. Model erosi yang sederhana namun telah memperhitungkan secara sistematis proses terjadinya erosi. menjadi sebuah prasyarat di suatu daerah yang sangat minim akan ketersediaan data. Tujuan utama dari penelitian ini adalah mengkorelasikan antara kerugian ekonomi ke dalam sebuah analisa resiko erosi tanah yang berdasarkan pada peta bahaya erosi. Penelitian ini didukung oleh basis data

The soil erosion risk should be assessed since it becomes an issue of long term disaster which has been causing many negative impacts. Part of that issue is responded by this study which endeavors to give another overview for obtaining the soil erosion risk method. Obtaining such reliable result of soil erosion risk requires accurate information of soil erosion hazard. The complexity of soil erosion hazard assessment has made some uncertainty in its value which depends on the type of measurement approach. Regarding the efficiency of the time and financial aspect, modeling in soil erosion is the most being developed among the approaches. Considering the availability of data, a model which simple but has already considered the complete process of erosion is needed in such poor data environment area. The main aim of this study is to correlate between the financial losses into a soil erosion risk approach based on the soil erosion hazard maps. In order to get a detail result, topography and land use map in scale of 1:5.000 of a sub-catchments area inside the Progo Watershed, Central Java, Indonesia is used as base maps of this study. MMF as soil erosion model which has considered the flowing process of erosion and can work in the poor data environment is used to determine the soil erosion hazard map. The reliability of the model’s result is validated with the actual erosion of the study area. The actual erosion is derived from the soil loss indicator evidence in the field. There are two soil loss indicators, which are used as validation i.e. rill erosion and sediment in drain. The financial loss is approached by the N2 loss caused by soil erosion. The cost of N2 loss is compared with the fertilizer price in the market. Based on the total hazard map, during 2005 the study area has lost 146.2 ton of soil which is equal to Rp 1.140.000,-. This result might be as a logic result, moreover the soil erosion hazard map is statistically can be accepted until 0,05 significance level. December is the highest risk month which prone to soil erosion. It has 99,095 ton of soil loss which equal to Rp714.500,- if compared with the N2 loss. Agricultural land is kind of land use in the study area which has high erosion rate. The vegetations which have small percentages of canopy e.g. spring onion, celery, snow peas, and string bean, conduct more soil erosion rate rather than other type of vegetation in the study area.

Kata Kunci : Erosi Tanah,Perhitungan Resiko, risk assessment, soil erosion modeling, erosion cost